#include <bits/stdc++.h>
using namespace std;
const int N = 510;
int n;
int f[N][N];

int main() {
	cin >> n;
	for (int i = 1; i <= n; ++i) {
		for (int j = 1; j <= i; ++j) {
			cin >> f[i][j];
		}
	}
	for (int i = n; i > 0; --i) {
		for (int j = 1; j <= i; ++j) {
			f[i][j] += max(f[i + 1][j], f[i + 1][j + 1]);
		}
	}
	cout << f[1][1] << endl;
	return 0;
}